There are numerous quality tests for yarns and the fabric they will produce. One such test is for the general appearance of the fabric. This test is accomplished by weaving or knitting the subject yarns into a fabric sample. Yarn quality defects and effects, such as color inconsistencies, width inconsistencies, hairiness, slubs, broken ends, and other novelty effects can thereby be judged as they will affect fabric quality, unarguably the most critical aspect of the yarn. The occurrence of yarn defects in close proximity on the fabric, of undesirable defect patterns, of a multitude of marginally acceptable yarn defects creating an unacceptable fabric defect, can be visually observed and quantified. This test has been standardized as ASTM D2255/90 and ASTM D2255. It has become the accepted method for predicting the quality of fabric to be produced from entire lots of sampled yarns based on the probability that unacceptable fabric defects will be observed in a sample of this size.
Fabric quality will be affected by other factors as well as yarn quality, such as loom defects. Because looms and knitting machines intended for high production runs of fabric cannot practically be interrupted for the running of small test runs, as reasoned below, the machines used for test sample runs tend to be smaller, older, worn, or obsolete models whose results would be generally unacceptable for producing marketable fabric. Variations in tension on one or more yarn strands during weaving or knitting will cause fabric variations that might be read as resulting from poor yarn quality. Sinusoidally occurring loom inconsistencies will cause recurring fabric faults whose regularity may not be recognized in the small test sample, and may therefore be read as resulting from poor yarn quality. Other loom deficiencies and also ambient temperature and humidity conditions may affect fabric quality independently of the quality of the yarn from which it was produced. Obviously, the grading of yarn in fabric samples is a somewhat qualitative process, leaving the possibility that one grader might judge a sample quite differently than another grader, that the subject sample might not accurately represent the fabric to be produced, or that defects will be missed as a result of the small sample size.
Other drawbacks to the current grading system are that it requires the actual weaving or knitting of a fabric sample, or winding the yarn on a board, which requires specialized equipment and specialized operator training, or an actual loom or knitting machine. Test samples can be produced using an instrument such as a Fiber Analysis Knitter (FAK) like that manufactured by Lawson-Hemphill, Inc., of Central Falls, R.I. Looms and knitting machines are huge and complicated machines requiring many manual settings and adjustments independent to each run. These machines cannot practically fit within small quality labs and require operator expertise not typical of lab personnel. A significant amount of the time taken to produce a fabric run is in the set-up of the machine. Each fabric pattern requires a different loom set-up procedure. Looms are quite expensive to purchase and operate, take up substantial floor space, and must be used efficiently in the production of marketable fabric in order to justify their high cost. For reasons of time and cost, the practice of setting-up a production loom to run a few small test samples of a particular fabric would be impractical. Test samples are generally run on smaller weaving or knitting machines which are more practical for this application even though those tend to be slow and to have outputs which may not be fully indicative of production fabric.
Further drawbacks to the current test sample making method is that many actual yarn sample spools are required to run even these small test samples, and the yarn waste percentage is very high on such a short run.
It can readily be seen that the current fabric grading method is very slow, inaccurate, labor intensive, highly judgmental and expensive.